The plaques of Alzheimer disease (AD) are seen here with a silver stain. In AD there are extracellular deposits of Aß. In the more numerous, smaller diffuse plaques this Aß alone is present as filamentous masses. However, the diagnostic neuritic plaques also have dystrohic dilated and tortuous neurites, microglia, and surrounding reactive astrocytes.Such plaques are most numerous in the cerebral cortex and hippocampus. This dementia is marked mainly by progressive memory loss.